Regarding your second point I think there are two cases here that should be kept separate. The first is that you are teleported into a parallel dimension where

Regarding your second point I think there are two cases here that should be kept separate. The first is that you are teleported into a parallel dimension where literally everything works differently from here. In that case I do agree that there are several reasonable choices of models of computation. You simply have to pick one and hope it wasn't too bad. But the second case is that you encounter some phenomenon here in our ordinary world. And in that case I think you can do way better by reasoning about the phenomenon and trying to guess at plausible mechanics based on your preexisting knowledge of how the world works. In particular, I think guessing that "there is some short natural language description of how the phenomenon works, based on a language grounded in the corpus of human writing" is a very reasonable prior.